U.S. Pat. No. 6,972,464 (Patent Document 1), U.S. Pat. No. 6,713,823 (Patent Document 2), U.S. Pat. No. 6,278,264 (Patent Document 3) and Japanese Patent Application Laid-Open Publication No. 8-255910 (Patent Document 4) describe techniques related to a semiconductor device having a MOSFET. Japanese Patent Application Laid-Open Publication No. 2010-16035 (Patent Document 5) describes a technique related to a semiconductor device for a DC-DC converter.